diff --git a/loopy/codegen/instruction.py b/loopy/codegen/instruction.py
index c490abb6ed1635c135fc77468f27cd833b1d57b2..6224d9709f5f796f84c3fd177125e0703d92d173 100644
--- a/loopy/codegen/instruction.py
+++ b/loopy/codegen/instruction.py
@@ -221,7 +221,7 @@ def generate_call_code(codegen_state, insn):
 
     if codegen_state.vectorization_info:
         if insn.atomicity:
-            raise Unvectorizable("function call")
+            raise Unvectorizable("atomic operation")
 
     # }}}
 
diff --git a/loopy/kernel/instruction.py b/loopy/kernel/instruction.py
index 90be2f409fa9fb1e363df8f56d62d7d9e8e4e54f..4477f5bafc7dab867af63d5152f9cbdec12a0dda 100644
--- a/loopy/kernel/instruction.py
+++ b/loopy/kernel/instruction.py
@@ -994,6 +994,13 @@ class CallInstruction(MultiAssignmentBase):
             else:
                 key_builder.rec(key_hash, getattr(self, field_name))
 
+    @property
+    def atomicity(self):
+        # Function calls can impossibly be atomic, and even the result assignment
+        # is troublesome, especially in the case of multiple results. Avoid the
+        # issue altogether by disallowing atomicity.
+        return ()
+
 # }}}